The invention concerns an arrangement for the presenting of weft threads in a rapier weaving machine, and a rapier weaving machine having such an arrangement.
In EP-A-421 394, an apparatus is described which has two clamping positions. After the delivery of the weft thread to the rapier weaving-machine, the appropriate clamping position is made ready for the taking-up of the inserted weft thread in the manner of a weft selector and finally clamps the weft thread, with the clamping positions being arranged above and below the cloth plane. There is provided a first guide member having a slit through which the weft threads are guided from the weft thread presenting devices to the clamping positions. Due to the fact that the weft threads are guided in the same plane but are clamped at different levels on both sides of this plane, contact between the weft threads and crossing-over of the weft threads occurs in the slit and in the tracks of the weft threads between the clamping positions and the weft thread presenting devices respectively. This is a disadvantage. In one embodiment of the apparatus, the end of the slit is widened to prevent of the weft thread from being pulled along. When the presented weft thread is taken over by the gripper, the thread is stretched over the edge formed by the widened portion, which can lead to breakage of the weft thread. Apart from this, the tracks of the weft threads can cross. These are further disadvantages.
For the presenting of a plurality of weft threads, for example, of four weft threads, two such devices are provided. The devices are arranged in an upper and lower position and each is movable up and down in order to displace the respective device into a presenting position. The time-interval between two weft thread presenting procedures is thereby increased, in particular due to the displacement of the device, so that the working speed and the number of presented weft threads is undesirably restricted. Since every device comprises a thread guide, the weft threads in each device are shifted with respect to the weaving plane such that each thread has an excess length which can lead to a crossing-over of the weft threads. In particular, loops occur with metal thread composite material in the form of bands (Lurex), highly spun crepe yarns, microfibers, etc.
Since the two devices work according to the principle of a weft selector, the apparatus for presenting a plurality of weft threads is expensive and the space required is large, which represents a further disadvantage.